In this review, we highlight the use of organic photoredox catalysts in a myriad of synthetic transformations with a range of applications. This overview is arranged by catalyst class where the photophysics and electrochemical characteristics of each is discussed to underscore the differences and advantages to each type of single electron redox agent. We highlight both net reductive and oxidative as well as redox neutral transformations that can be accomplished using purely organic photoredox-active catalysts. An overview of the basic photophysics and electron transfer theory is presented in order to provide a comprehensive guide for employing this class of catalysts in photoredox manifolds.

Organic Photoredox Catalysis

N-Heterocyclic Carbenes in Late Transition Metal Catalysis

Asymmetric enamine catalysis.

Reactions that convert carbon–hydrogen (C–H) bonds into carbon–carbon (C–C) or carbon–heteroatom (C–Y) bonds are attractive tools for organic chemists, potentially expediting the synthesis of target molecules through new disconnections in retrosynthetic analysis. Despite extensive inorganic and organometallic study of the insertion of homogeneous metal species into unactivated C–H bonds, practical applications of this technology in organic chemistry are still rare. Only in the past decade have metal-catalyzed C–H functionalization reactions become more widely utilized in organic synthesis.Research in the area of homogeneous transition metal–catalyzed C–H functionalization can be broadly grouped into two subfields. They reflect different approaches and goals and thus have different challenges and opportunities. One approach involves reactions of completely unfunctionalized aromatic and aliphatic hydrocarbons, which we refer to as “first functionalization”. Here the substrates are nonpolar and hydrophobic a...

Weak coordination as a powerful means for developing broadly useful C-H functionalization reactions.

Small-molecule H-bond donors in asymmetric catalysis.

The regioselective protonation of acyclic polyene was achieved, dependent on the choice of catalyst. The addition of myrcene to trimethylhydroquinone, using boron trifluoride–diethyl ether (1/1), predominantly gave a spiro structure. When (+)-10-camphorsulfonic acid was used as a catalyst, the major compound produced was chroman.

Direct Construction of the Chroman Structure from 1,3-Diene. Regioselective Protonation of Acyclic Polyene

Separation of the cyclization and rearrangement processes of sterol biosynthesis. Enzymic formation of a protosterol derivative

Asymmetrization of meso-cyclic ketones using homochiral acetal templates

The title synthesis involves (1) epoxidation of allylic alcohols with t-butyl hydroperoxide in the presence of vanadium catalyst followed by trimethylsilylation, (2) specific oxirane ring opening by means of diethylaluminum 2,2,6,6-tetramethylpiperidide and subsequent desilylation producing 3-ene-1,2-diols, and (3) removal of both hydroxyl groups through bromination with a mixture of phosphorus tribromide and copper(I) bromide and the successive zinc debromination. The sequence of reactions has been extended with considerable success to the preparations of β-myrcene from nerol, trans-β-ocimene from geraniol in a specific way, and α and β-farnesenes from their biological precursors. A C12 sex pheromone of red bollworm moth has been prepared efficiently by this method with cyclododecene as a starting material.

A Highly Stereospecific Procedure for the Transformation of Allylic Alcohols into 1,3-Dienes

Separation of the cyclization and rearrangement processes of lanosterol biosynthesis. Enzymic conversion of 20,21-dehydro-2,3-oxidosqualene to a dehydroprotosterol.

Hisashi Yamamoto

Papers

Direct Construction of the Chroman Structure from 1,3-Diene. Regioselective Protonation of Acyclic Polyene

Separation of the cyclization and rearrangement processes of sterol biosynthesis. Enzymic formation of a protosterol derivative

Asymmetrization of meso-cyclic ketones using homochiral acetal templates

A Highly Stereospecific Procedure for the Transformation of Allylic Alcohols into 1,3-Dienes

Separation of the cyclization and rearrangement processes of lanosterol biosynthesis. Enzymic conversion of 20,21-dehydro-2,3-oxidosqualene to a dehydroprotosterol.